Scientists from Spain have developed an electrolumines method for daylight that uses other strings to supply electricity to the inspected string. It was simulated and then tested in two PV plants of 50 MW. Comparative assessment against Lab electruminuminia resulted in acceptable diagnostic performance.
A research team at the Spain’s University of Valladolid has created a new self-powered daylight electroluminescence (Del) for PV system inspections.
DEL usually requires power sources such as generators or bidirectional inverters to inject power during a string inspection. However, the new methodology is self-laid out by using other PV strings in the plant to deliver the necessary current.
“Within PV diagnostics, D has emerged as a promising solution, which makes EL inspections possible during the day with high quantity efficiency (QE) infrared cameras (eg ingaas) and ambient lightlatration,” the group said. “However, it still requires the current injection, which offers logistical and economic challenges. This work introduces a new self-leading method for DEL inspections using other PV strings to provide. This minimizes external electricity needs, reducing the costs and the impact of the environment.”
The methodology labels the string that drives as SP and the string that must be measured as SM. SP must have a larger number of modules in a series to inject the required current for an EL image, that is, in the range of 80-100% of the short -circuit current (ISC). Performing simulations in the LTSpice software, the effect of removing one, two, three and four modules from a first 30 modules from SM was simulated. According to the results, no more than two modules may be removed in such a configuration.
After the automated simulation, the group carried out experimental tests for two commercially working 50 MW solar plants in Spain.
The first factory had C-SI modules of 435 W and an efficiency of 19.7%, while the second MC-SI modules of 345 W had an efficiency of 17.4%. The first had 12 strings per combination, with 28 modules per string, while the second 30 modules had per string and 24 strings per combination. In both cases, the entire string consisted of modules in two rows, mounted on tables with an automated mobile axis.
Image: Universidad de Valladolid, Solar Energy, CC by 4.0
“A device that is called an electronic switching device (ESD) is connected between the SP and SM belts. This device, developed by our research group, acts as a switch between the two sets of strings (SP and SM), in which two states are obtained on SM: on state and outside,” explained the scientists.
“Measurement consists of taking a number of images with the INGAAS camera, as an alternative electric connect (on status) and disconnecting (off -status) the SP to SM, which is carried out by means of the switching and operating device. Our system includes Synchronized switch between the current injection (via) camera.”
The measurements were taken throughout the year, with irradiation ranging from 200 W/m2 to 1,000 W/m2, and temperature ranging from 4 C to 37 ° C. To analyze the quality of the Del images, some modules were dismantled and sent for detailed inspection with the help of a high-resolved inspection.
“The comparison of the Del images against lab-EL images shows a significant difference in image quality (lower in the Del), which comes from multiple technical factors: limitations of sensor resolution, simultaneous imaging requirements with double module and complexities of field measurement under operating conditions with high irradiation, the group concluded. “Nevertheless, a comparative assessment against Lab-EL standards reveals acceptable diagnostic performance with effective defect detection options.”
The new methodology was presented in “Electroluminescence inspections of PV modules and strings through a self-powerful configuration in daylight mode“Published in Solar energy. Scientists from the Spain’s University of Valladolid, Cobra Installations and Services (Cobra Instalaciones Y Servicios) and the University of Burgos participated in the study.
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